There are about 20 supervolcanoes on Earth. But the term is criticized by researchers – experts do not see an acute danger.
Magma bubbles beneath the vineyards and thermal baths of southern Italy, forming one of the most active volcanic systems in the world, in a region known as Campi Flegrei.
Outside Naples, the Campi Flegrei is not a typical volcanic mountain, but rather a bowl-shaped depression dotted with craters. Smelly steam rises from vents, mud bubbles from pools and small earthquakes shake hundreds of thousands of residents living at the mouth of the volcano. Mythology says that Campi Flegrei, which means “burning fields” in Italian, is associated with the gates of hell.
It is also known as a supervolcano – a rare but unofficial name for volcanoes that have caused the most powerful eruptions in Earth’s history. The Campi Flegrei supereruption occurred about 39,000 years ago (as determined by rock records) and spewed gases and nearly a trillion gallons of molten rock, blocking sunlight and causing severe cooling. The most recent, much smaller eruption occurred in 1538 and created a mound of earth about 120 meters high.
Months of seismic activity at Campi Flegrei – more than 2,500 magnitude 4.3 earthquakes since September – have raised fears that the volcano could soon erupt again. But researchers say supervolcanoes don’t work that way and doubt a prophetic eruption.
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What does it mean to be a supervolcano?
“When a volcano is called a supervolcano, what it really means is that it has had a supereruption at least once in the past,” says Christopher Kilburn, a volcanologist at University College London. “But that doesn’t mean there will be more supereruptions in the future. . . . Very, very large eruptions are much, much rarer.”
Scientists can’t see what’s happening below the surface of Campi Flegrei with the naked eye, but Kilburn said the recent activity could be underground molten rock and fluids realigning themselves. These movements become visible on the surface as earthquakes.
“That in itself does not mean there is an outbreak,” Kilburn said. The volcano has exhibited ground deformation and earthquakes in the past, but no eruptions have occurred. But as activity resumes after a long time, “it is natural to be a little worried that this could happen”.
There are only about 20 supervolcanoes on Earth
Of the more than 1,000 known volcanoes in the world, only about 20 are so-called supervolcanoes. Technically speaking, they are those that have the highest score on the volcanic explosiveness index, which varies from V0 (non-explosive) to V8 (colossal eruptions). Such a supereruption ejects a volume of about 1,000 cubic kilometers or more – about a thousand times larger than Mount Saint Helens (V5), which caused landslides, fires, floods and more than 50 deaths in 1980.
The last eruption of V8 occurred about 27,000 years ago in Taupo, New Zealand. These violent volcanic eruptions typically leave behind a depression called a caldera, rather than a volcanic cone. According to Kilburn, this is because eruptions expel a large amount of material – molten rock stored several kilometers below the surface – in a very short period of time. The ground becomes unstable and sinks.
If you don’t pay attention to these dips, you might miss them, he says.
“You can drive a car through the boiler and come out the other side without realizing you’ve done just that, because the changes are quite smooth,” Kilburn said.
After the massive eruption ends, Kilburn says the volcano returns to “normal,” sometimes producing full-sized eruptions at the bottom of the caldera. In other words, a supervolcano has nothing to do with “super” once it erupts, so the term is somewhat misleading.
Yellowstone is one of the most famous supervolcanoes in the world
Yellowstone, one of the world’s most famous supervolcanoes, measures 30 by 45 miles and attracts millions of tourists to its park. Its largest eruption occurred 2.1 million years ago and ejected more than 2,400 cubic kilometers of material. As with many caldera systems, most of Yellowstone’s eruptions since then have been much smaller.
Supervolcano is a made up word
Supervolcano is “a made-up word,” says volcanologist Michael Poland, senior scientist at the Yellowstone Volcano Observatory. “I think it’s misleading. I think it is being misapplied. I can’t stand that term. I wish it went in the trash can, but it’s too sexy.”
Just like Superman or Superstar, Supervulkan also sounds too Hollywood for your taste. It implies an apocalyptic-type explosion, but as far as we know, no explosive volcanic eruption has ever caused a mass extinction, he said.
The largest volcanic explosion in the geological record is believed to have occurred about 74,000 years ago in Toba, Indonesia, and reached V8 on the volcanic explosivity index. Some scientists initially speculated that the eruption nearly wiped out humanity because populations declined shortly afterward, but archaeological evidence showed that Homo sapiens thrived in more distant locations after the eruption.
“No explosive volcanic eruption that we know of has ever been associated with a mass extinction of plants or animals,” said Poland, who is also a scientist at the U.S. Geological Survey (USGS). “But that doesn’t mean it wouldn’t be devastating or difficult to survive.”
What would happen in a Yellowstone supereruption?
Many speculate about what would happen if there were another Yellowstone supereruption. According to the USGS, neighboring states would be hit by fast, hot avalanches of volcanic ash, pumice, gases and rocks. Ashes can remain hundreds of kilometers away and be transported around the world. Tiny aerosol particles emitted by the volcano would reflect sunlight back into space, causing cooling on the Earth’s surface and affecting agriculture.
But scientists are skeptical that a supereruption could happen again in Yellowstone. According to the USGS, the volcano may not even have enough molten magma beneath its caldera to trigger an eruption.
Furthermore, Kilburn does not believe that “anyone believes there will be another supereruption” at Campi Flegrei in the near future. However, a smaller eruption could have a significant impact, since more than 1 million people live in and around the area. Local authorities issue warnings and prepare evacuation plans depending on the volcano’s activity.
Local officials need to “consider the possibility of an outbreak,” Kilburn said. “I’m not saying it’s likely, but they would be remiss if they ignored that possibility.”
About the author
Kasha Patel writes the weekly Hidden Planet column, which covers scientific topics surrounding Earth, from our inner core to space storms heading toward our planet. She also reports on weather, climate and environmental issues.
We are currently testing automatic translations. This article has been automatically translated from English to German.
This article was first published in English on November 10, 2023 on “Washingtonpost.com” – as part of a cooperation, it is now also available in translation for readers of the IPPEN.MEDIA portals.